Can you get a picture of the swollen hocks? A PCR test for mycoplasma synovitis is the best method of testing. Your state vet may be able to help with that, or you could contact a lab called Zoologix to help. Here is some more reading:
https://waddl.vetmed.wsu.edu/2022/11/10/mycoplasma-synoviae-fact-sheet/
https://waddl.vetmed.wsu.edu/2022/11/10/mycoplasma-synoviae-fact-sheet/